So, we're talking about pheochromocytoma.
I think this is probably something that we've all learned about but hardly any of us see
but it's exciting, nevertheless, when you do see it clinically
and you should be aware of what it looks like so you can urgently treat these patients as they need this.
Pheochromocytoma are catecholamine-secreting tumors that arise
from the chromaffin cells of the adrenal medulla and sympathetic ganglia.
Patients clinically typically will present with this classical triad in addition to hypertension.
They have episodic headache, diaphoresis or sweating, tachycardia,
sometimes they explain this impending sense of doom.
Now, I want you to keep in mind that 40% of the population or 40% of tumors
are going to be part of a familial disorder including multiple endocrine neoplasia type 2 or MEN2,
von Hippel-Lindau syndrome, and neurofibromatosis type 1.
So, getting a family history is going to be critical in that patient population.
So, once we suspect pheochromocytoma, our next step in diagnosis
is to do a 24-hour fractionated urinary metanephrines and catecholamines.
What we're looking for is norepinephrine, epinephrine, dopamine, and normetanephrines.
Now, this has a very high sensitivity and specificity, about 98% respectively.
We can also do something like a fractionated plasma metanephrines.
It has a very high sensitivity between 96 and 100% but specificity is quite a bit lower
because there's a lot of false positives here.
It's much more attractive to patients because it doesn't require a 24-hour urine.
It's something that you can just get a plasma level from.
But really, you should only use this first-line when your pre-test probability is high.
So, I might reserve this for somebody who has classical symptoms
and a familial history like MEN2.
Alright, once we've got biochemical confirmation,
remember, we have to locate where this tumor is so we want to do
either a CT or MRI of the abdomen and pelvis.
This allows us to detect almost all sporadic tumors cuz most are about 3 cm or larger in diameter.
The sensitivity is quite high at 98-100% but only 70% specific,
again, this is because of that prevalence of adrenal incidentalomas.
That means there's an adrenal tumor there that's nonfunctional.
We've talked about those before in our other cases.
Now, if for some reason, we don't have any luck with our CT or MRI imaging,
we can go to our radionuclear testing with an MIBG scintigraphy.
This is performed, again, if we have a CT that's negative and/or an MRI that's negative
but we have biochemical confirmations so we know that a pheochromocytoma is there.
This particular test can also detect multiple tumors
so if a patient has multiple tumors up the sympathetic ganglia, we can see that.
And the radioisotope is essentially of norepinephrine so it's a norepinephrine analog.
Okay, so once our patient manifest, we have biochemical confirmation,
we now have location of where the tumor is. What do we want to do?
Before we do anything, we've got to control that blood pressure.
These patients have some of the highest blood pressures
and they really can succumb to that and have complications.
So, we want to get an alpha antagonist on board
and before we even think about surgical resection,
that blood pressure needs to be controlled as best as we can do that.
So, we're gonna use something like phenoxybenzamine
which is a long-acting nonspecific alpha-blocking agent.
We typically start that about 7-10 days prior to surgical resection.
We can also use phentolamine which is a shorter-acting nonspecific alpha-blocking agent as well.
Now, we can use beta blockers because remember, these patients are extraordinarily tachycardic
but we only want to use these after adequate alpha blockade is achieved. Okay?
If we start beta blockers before we have alpha blockade,
we have unopposed alpha stimulation and those patients can get extraordinarily hypertensive.
So, please remember, long-acting alpha antagonist first followed by beta blockade.
Now, if additional agents are needed, the use of dihydropyridine calcium channel blockers can be used.
Things like nifedipine or amlodipine.
Now, we now -- once our blood pressure is fairly well-controlled,
we wanna get our endocrine surgeon or surgical colleague to come in and remove the tumor.
One thing that I do want you to be aware of is that patients
can undergo acute hypertensive crisis when you are in the process of surgically resecting this tumor.
This can occur because of endotracheal intubation
with anesthesia induction or just manipulating that adrenal gland.
So, during the operative procedure, it's important to control that blood pressure,
those patients should be treated with parenteral nitroprusside, phentolamine, or nicardipine.